Filtering apparatus

ABSTRACT

A filtering apparatus with a plurality of filtering elements ( 9 ) which can be accommodated in a filter housing ( 1 ) having a filter inlet ( 45 ) for fluid to be filtered and a filter outlet ( 43 ) for the filtered fluid, wherein during the filtration operation, at least one of the filtering elements ( 9 ) can be back-flushed by means of a back-flushing device ( 13, 21 ) in order to dedust the effective filtering surface of said filtering element, the back-flushing device comprising a pressure control device ( 13 ) for assisting the back-flushing operation, is characterized in that the pressure control device comprises a hydraulic accumulator ( 13 ), the one fluid chamber ( 67 ) of which can be filled during the filtration operation with a quantity of dedusted fluid and can be connected for a back-flushing operation via a back-flushing guide ( 21 ) to the clean side ( 59 ) of the filtering element ( 9 ) to be dedusted, and in that, for a back-flushing operation, a further fluid chamber ( 79 ) of the hydraulic accumulator ( 13 ) can be subjected to a media pressure in order, by means of a resultant movement of the separating element ( 65 ) of the hydraulic accumulator ( 13 ), to at least partially again dispense the filling amount of the dedusted fluid for the back-flushing operation from the first fluid chamber ( 67 ).

The invention relates to a filtering apparatus with a plurality of filtering elements that can be accommodated in a filter housing having a filter inlet for fluid that is to be filtered and a filter outlet for the filtered fluid, wherein, during the filtration operation, at least one of the filtering elements can be back-flushed by means of a back-flushing device, which contains a pressure-control device for supporting the back-flushing operation, in order to clean the effective filtering surface of said filtering element.

A filtering apparatus of this class is disclosed in DE 10 2007 054 737 A 1. Such a filtering apparatus allows for continuous filtration operation, wherein successive filtering elements that must be regenerated are back-flushed, while the filtration operation is continued by means of the remainder of the filtering elements, such that the filtration operation is never interrupted.

In the known filtering apparatus, the back-flushing operation does not only occur in such a manner that, during the back-flushing phase, the system pressure, which is present inside the filtering apparatus, causes a partial flow of the filtrate to flow in the reverse direction through the filtering element that is to be cleaned in order to loosen and remove dirt from the element; instead, with the goal of being able to remove more persistent impurities as well, a pressure-control means is used on the respective filtering element that is to be back-flushed in order to create a vacuum. Therefore, the back-flushing operation is not only subject to the effective system pressure but also to the effect of the pressure control, whereby a higher pressure gradient is available for loosening impurities.

On the filtering apparatus that is known in the art, the pressure-control device includes a locking element that is able to block the fluid connection between the fluid that flows into the filter housing and that is to be filtered and the respective filtering element that is to be back-flushed during a back-flushing operation. Prior to the back-flushing process, this results in an interruption of the fluid flow that enters the filtering element, such that the flow rate, which is in effect at the time of the locking process, generates, by way of a flow-dynamic effect, a suction effect. Consequently, the back flow of the filtrate on the clean side of the respective filtering element is not only supported by the system pressure, but the back-flow of the filtrate is intensified by the post-suction effect, which is available due to the dynamic effect resulting from blocking out the flow that flows in from the untreated side.

However, the magnitude of the hydrodynamic effect that is achieved by the locking process depends on the flow rate and is, therefore, correspondingly limited. In application fields where tough contaminations must be expected that are difficult to loosen from the filtering surface, there exists the risk, therefore, that the hydrodynamically supported back-flushing effect is not completely satisfactory.

In view of this problem, it is the object of the present invention to provide a filtering apparatus that is able to achieve a particularly effective back-flushing effect, which is supported by pressure control.

According to the invention, this task is achieved by a filtering apparatus that has all the characteristics as specified in claim 1.

A crucial special aspect of the invention is, therefore, the fact that the pressure-control means contains a hydraulic accumulator with one fluid chamber that can be filled with a quantity of cleaned fluid, while the apparatus operates in the filtration operation, and can be connected, via a back-flushing guide, to the clean side of the respective filtering element that must be cleaned for a back-flushing operation. Applying pressure to the further fluid chamber of the hydraulic accumulator causes the thus effected movement of the separating element of the hydraulic accumulator to eject the filling volume of the fluid, which reaches the filtering element that is to be cleaned via the back-flushing guide, as a back-flushing fluid.

By selecting the media pressure that is used inside the hydraulic accumulator for moving the separating element, the user is able to optimally adjust the flow rate of the back-flushing fluid that reaches the filtering element via the back-flushing guide to the circumstances that apply; meaning, the media pressure can be selected such that, by adjusting the same to the type of filter medium, it is possible to achieve an optimal back-flushing effect. In particular, with comparatively pressure-resistant filtering elements, such as tapered or cylindrical slotted-screen tube elements, it is possible to work at high pressure levels, and therefore high flow rates, in the hydraulic accumulator, thereby loosening even tough impurities from the filter surface.

In advantageous embodiments, the further fluid chamber of the hydraulic accumulator for the back-flushing operation can be connected to a media pressure source for the back-flushing operation by means of a valve control means, particularly in the form of a compressed air source. In many instances, the use of compressed air can be especially advantageous, for example when the filtering apparatus is operated in connection with systems or facilities that are provided with a compressed air supply. It is understood that other gaseous media, mixtures of gas and alcohol as well as mixtures of fluids and solids, could be envisioned as pressure media. In addition, particularly in underwater facilities, such as deep-sea drilling applications, it is possible to use sea water as a pressure medium that is subject to deep-sea pressure.

In especially advantageous embodiments, the hydraulic accumulator and the back-flushing guide are connected to each other, rotatably disposed inside the filter housing, and movable, to execute adjustment movements between filtration operation and back-flushing, by means of a rotary drive. An arrangement of this kind facilitates a particularly simple and compact structural assembly, in that a drive is mounted on one free and easily accessible end of the hydraulic accumulator in the form of an electrical gear motor that transfers the rotary movement via the hydraulic accumulator to the back-flushing guide, which is disposed further to the inside of the apparatus, adjusting the same in the rotary positions, in which the fluid connection is established, to the filtering element that is to be cleaned.

Particularly advantageously, the hydraulic accumulator is envisioned as a piston accumulator that can be rotated around the cylinder axis together with the back-flushing guide, which is disposed on one cylinder end. In comparison to other types of accumulator constructions, such as diaphragm accumulators, spring accumulators, bellows accumulators and the like, aside from their robust construction, piston accumulators are characterized by the good ratio between the structural size and filling capacity of cleaned fluid than can be accommodated, which corresponds to the total stroke of the piston, and therefore, approximately the total volume of the accumulator cylinder.

Especially advantageously, the filtering elements can be accommodated in their own element chambers, which are disposed inside the filter housing on a circular line forming a concentric circumference around the cylinder axis.

With this type of a concentric arrangement, the hook-up connections of the individual element chambers to the rotatable back-flushing guide can have an especially simple design.

Especially advantageously, the arrangement therein is provided in such a way that the element chambers include a first chamber hook-up, which is connected to the clean side of the filtering element, and a second chamber hook-up, which is connected to the untreated side, and that both hook-ups are open toward a main chamber of the filter housing, with the rotatable back-flushing guide extending into said main chamber as a switching organ, and the adjusting movements of which control the inflow and outflow of fluid to and from the first and second chamber hook-ups for the back-flushing operation.

To provide a particularly compact structural assembly, it is possible for the back-flushing guide to function as a separating organ as well, which separates the main chamber of the filter housing into a filtrate part that includes the filter outlet and a non-filtrate part that includes a filter inlet. With larger nominal widths of the filter and long filtering elements, it can be advantageous to integrate the piston accumulator in the switching organ of the rotatable back-flushing guide between the first chamber hook-up, which is connected to the clean side of the filter element, and the second chamber hook-up, which is connected to the untreated side, or even to dispose the same externally and connect it by means of a channel for the back-flushing medium to the switching organ. To this end, the arrangement is provided such that the back-flushing guide includes, with an axial spacing from the piston accumulator and the opposite end thereto, an annular body, having a circumferential radial seal that forms a radial projection dividing the main chamber, together with the wall of the main chamber, into a filtrate part and a non-filtrate part.

With regard to the switching function that the back-flushing guide performs during the rotational movement thereof, the arrangement can be provided such that the mouths of the first and second chamber hook-ups of the element chambers are disposed on a wall of the filtrate part and/or non-filtrate part that constitute a cylinder area, and that, when changing to the back-flushing operation, hook-up ends that project from the cylinder axis, respectively, from the inflow and outflow lines, which are formed on the back-flushing guide, become congruent with the chamber hook-ups, wherein the inflow line constitutes the connection of the first fluid chamber of the piston accumulator with the first chamber hook-up and the outflow line constitutes the connection of the second chamber hook-up with the back-flushing outlet of the main chamber.

Preferably, the back-flushing outlet can be blocked and released by means of a valve apparatus.

With regard to the valve means that control the activity of the hydraulic accumulator, the apparatus can be advantageously provided such that a valve, which can be actuated by a pressure means, is present, preferably in form of a 5/2-way valve, that controls the connection of the fluid chamber of the hydraulic accumulator, which can be pressurized by the pressure medium, to the related pressure source.

An especially advantageous embodiment provides for a further valve, preferably in the form of a 3/2-way valve, disposed in the connection of the fluid chamber with the pressure source, that allows for optionally reducing the medium pressure.

In especially advantageous embodiments, the fluid chamber of the hydraulic accumulator that receives the quantity of the cleaned fluid can be filled via a flow-control means, which is disposed between the filtrate part of the main chamber and the inflow line of the back-flushing guide. This way, it is ensured that the filling process takes place each time without a drop in the system pressure, due to a major, branched off volume flow that is accompanied by the corresponding reduction of the filtrate volume flow released by the device.

The invention will be described in further detail below based the drawings. Shown are as follows:

FIGS. 1A to 1D are perspective views of the filtering apparatus represented by way of one embodiment with two, three, four or five filtering element chambers, respectively, shown at an angle and drawn in a schematically simplified manner;

FIG. 2 is a longitudinal section of the central area of an element chamber, drawn on an enlarged scale in comparison to the FIG. 1, to illustrate the filtration operation;

FIG. 3 is a longitudinal section corresponding to FIG. 2, illustrating the operating state of the back-flushing means for the element chamber, as represented in a sectional view;

FIG. 4 is a partial longitudinal section, drawn as a sectional view on an enlarged scale as compared to FIGS. 2 and 3, of only the partial section of the embodiment that is adjacent to the piston accumulator valve; and

FIG. 5 is a partial longitudinal section similar to the one shown in FIG. 4, but in a rotated position of the sectional plane in relation to the former.

FIG. 1 depicts in the partial FIGS. 1A to 1D the overall view, respectively, of the filtering device according to the invention, where a main part of the housing is identified by the numeral 1, an accumulator part by the numeral 3 and a drive part by the numeral 5. FIG. 1 also illustrates that the device according to the invention can be configured in the manner of a modular assembly system for operation with a varying number of filtering elements. FIG. 1A shows an example with two filtering element chambers 7, with each being able to accommodate one filtering element 9 (FIGS. 2 and 3); FIG. 1B, on the other hand, shows an example with three filtering element chambers 7; FIG. 1C is an example with four element chambers 7; and FIG. 1D, finally, is an example with five element chambers 7. A filtering element can also be formed by a plurality of filter candles in a holder.

As can be derived from FIGS. 2 and 3, the accumulator part 3, taking the form of a hollow cylinder, is connected by a flange connection to the top open end 11 of the main part 1, and a piston accumulator 13 is coaxially disposed therein, such that the cylinder axis of said accumulator defines the vertical axis of the accumulator part 3. An intermediate space between the outside of the piston accumulator 13 and the jacket of the accumulator part 3 constitutes a gas pressure chamber 15, which is closed at the top end by a housing lid 17 and sealed at the bottom end, relative to the main part of the housing 1, by the circumferential rim 19 of a back-flushing guide 21, which forms, by the circumferential rim 19 thereof, a sealed apron at the bottom end of the cylinder 23 of the piston accumulator 13.

The back-flushing guide 21 extends away from the bottom open end of the cylinder 23, through a main chamber of the main part of the housing 1, to the base part 25 thereof, where a back-flushing outlet 27 is disposed, and the back-flushing guide 21 is sealed in relation to the same by a sealing element 28.

On the back-flushing outlet 27, there follows a back-flushing line 29 that can be blocked and opened by a motor valve 31. Approximately half way between the piston accumulator 13 and the end located at the back-flushing outlet 27, the back-flushing guide 21 includes an annular body 33, which forms a radial projection separating the main chamber of the main part of the housing 1, through which the back-flushing guide 21 passes, into a filtrate part 35 and a non-filtrate part 37. To provide a leak-proof separation, the annular body 33 includes a circumferential seal 39 that acts in conjunction with the interior wall 41 of the main chamber. The filter outlet 43 for the filtered fluid is disposed on the filtrate part 35, and the filter inlet 45 for fluid that is to be filtered is disposed on the non-filtrate part 37.

At the top end, as seen in the drawing, the cylinder 23 of the piston accumulator 13 is closed by an end piece 47 the top end of which is connected to a coupling piece 49, which is connected to the output shaft of a gear motor of the drive part 5. This way, it is possible to rotate the entire unit, comprising the piston accumulator 13 and back-flushing guide 21, as a whole, inside the accumulator part 3 and the main part of the housing 1, wherein a limit switch 51 is provided for controlling the rotary settings.

In FIGS. 2 and 3, one of the filtering element chambers 7 is visible in the sectional representation. Each element chamber 7 contains one filtering element 9 in the manner of a filter candle having a cylindrical or tapered shape. For example, a so-called slotted-screen tube element is also possible. FIG. 2 shows the operating state for the filtration operation of this filtering element 9, wherein, as illustrated by the flow arrows, the fluid, which flows in via inlet 45, enters the non-filtrate part 37, flowing around the back-flushing guide 21 and, via a chamber hook-up 53, which is disposed in the wall 41 of the main chamber of the housing 1, into the untreated side 55 of the element chamber 7. From there, the fluid flows through the filtering medium 57, from the outside to the inside, to the clean side 59 of the element chamber 7 that is closed by a chamber lid 61,

and from where the cleaned fluid reaches the filtrate side 35 via a chamber hook-up 63, exiting the apparatus via the filter outlet 43 thereof.

FIG. 2 shows that, in this operational state of the filtration, the piston 65 is located at the top end of the cylinder 23, and the fluid chamber 67, that is adjacent to the bottom side of the piston 65, has the greatest volume thereof. The chamber 67 therein, as indicated by the circular symbols with crosswise lines, is filled with a volume of cleaned fluid, wherein, during the filtration operation, this filling volume leaves the filtrate part 35 via a flow-control means 65 and enters the inflow line 71, which is configured on the inside of the back-flushing guide 21 and which is open at the end thereof that is directed toward the adjacent fluid chamber 67 of the piston accumulator 13. The other end of this inflow line 71 forms a hook-up end 73, which projects radially from the cylinder axis and which is closed in the filtration operation, as shown in FIG. 3, by resting against the inside wall 41 of the main part of the housing.

At the bottom end of the back-flushing guide 21, said back-flushing guide forms an outflow line 75 that corresponds to the inflow line 71 in terms of the structural form, which is connected to the back-flushing line 29 at the bottom end thereof, as shown in the drawing, and forms another radially projecting hook-up end 77 at the other end, which is closed, as shown in the rotational position of the back-flushing guide 21 according to FIG. 2, in the same manner as the other hook-up end 73, by resting against the wall 41.

In the operating state of FIG. 2, the fluid chamber 79, which is adjacent to the top end of the piston 65, has the smallest volume. This chamber 79 can be pressurized with compressed air for a back-flushing process, as depicted in FIG. 3, and said compressed air can flow from the gas pressure chamber 15 into the chamber 79 via a piston accumulator valve. In the representation as depicted in FIG. 2,

the valve piston 81 of the piston accumulator valve, that is movable within the end piece 47, is in the closed position thereof.

In FIG. 4, which shows further details of the piston accumulator valve, the valve piston 81 of the piston accumulator valve is in the upwardly moved open position, where the control rim 83 opens an air inlet 85 from the gas pressure chamber 15 to the fluid chamber 79 in order to drive the accumulator piston 65 downward. To this end, the valve piston 81 can be lifted by the generation of pressure in the valve chamber 87 in that a control pressure medium is supplied via a control line 89. For switching the piston accumulator valve into the closed position, there is a second control line 91 that opens into the valve chamber 87 at the top side of the valve piston 81. To actuate the piston accumulator valve, the control lines 89 and 91 are connected to a 5/2-way valve 93 (FIG. 6), which is, in turn, connected to a control pressure source, presently not shown. Compressed air can be supplied to the gas pressure chamber 15 via a compressed air hook-up 94 by a 3/2-way valve 95. A ventilation hook-up 97 in the directional valve 95 allows, when the piston accumulator valve is in the open position, a reduction of the gas pressure in the fluid chamber 79, such that the bottom fluid chamber 67 of the piston accumulator 13 can be filled, via a regulator means 69, with cleaned fluid during the filtration operation, and wherein the accumulator piston 65 moves upward.

FIG. 3 depicts the back-flushing means of the element chamber 7 in the operating state, as shown in a sectional representation. As depicted, the back-flushing guide 21 is in the rotational position where the hook-up ends 73 and 77 of the inflow line 71 and/or outflow line 75 are congruent with the chamber hook-ups 63 and/or 53 of the element chamber 7. The piston accumulator valve is in the open position, such that, as indicated by the flow arrows in FIG. 3, compressed gas flows into the fluid chamber 79 of the piston accumulator moving the accumulator piston 65 downward,

and the cleaned fluid in the fluid chamber 67 reaches the clean side 59 of the element chamber 7, as a back-flushing volume, via the inflow line 71, wherein a back-flushing flow of high intensity is generated by the compressed-air pressure and in effect, flowing through the filtering element 9 to be cleaned, from the inside to the outside, loosening dirt particles on the outside of the filter medium 57, such that the impurities are discharged via the outflow line 75 and the back-flushing outlet 27. The motor valve 31 releases the back-flushing line 29 for the back-flushing process. After the back-flushing process is complete, when the accumulator piston 65 reaches the bottom end position thereof, the back-flushing line 29 is locked again and the valve 95 terminates the compressed-air supply, while the valve piston 81 of the piston accumulator valve remains in the open position and the ventilation hook-up 97 on the directional valve 95 is open, such that the compressed-air pressure in the gas pressure chamber 15 and in the fluid chamber 79 is reduced again. In the context of the filtration operation that follows, the fluid chamber 67 is recharged, via the regulator means 69, with cleaned fluid, while the accumulator piston 65 moves upward. When this is the case, the piston accumulator valve is closed again by moving the valve piston 81 downward and resupplying the gas pressure chamber 15 via the directional valve 95 with compressed air while the ventilation hook-up 97 is closed, such that the apparatus is ready for a subsequent back-flushing process. 

1. A filtering apparatus with a plurality of filtering elements (9), which can be accommodated in a filter housing (1), having a filter inlet (45) for the fluid that is to be filtered and a filter outlet (43) for the filtered fluid, wherein, during the filtration operation, at least one of the filtering elements (9) can be back-flushed by means of a back-flushing device (13, 21), containing a pressure-control device (13) for supporting the back-flushing operation, in order to clean the effective filtering surface of said filtering element, characterized in that the pressure-control device contains a hydraulic accumulator (13), one fluid chamber (67) of which can be filled during the filtration operation with a volume of cleaned fluid and can be connected for a back-flushing operation, via a back-flushing guide (21), to the clean side (59) of the filtering element (9) to be cleaned, and in that a further fluid chamber (79) of the hydraulic accumulator (13) can be pressurized with a media pressure in order to again discharge, by means of a movement of the separating element (65) of the hydraulic accumulator that has been caused thereby, the filling volume of the cleaned fluid for the back-flushing operation, at least in part, from the first fluid chamber (67).
 2. The filtering apparatus according to claim 1, characterized in that, for the purpose of the back-flushing operation, the further fluid chamber (79) of the hydraulic accumulator (13) can be connected by a valve control means (81, 93, 95) to a media pressure source, particularly in the form of a compressed-gas source.
 3. The filtering apparatus according to claim 1, characterized in that the hydraulic accumulator (13) and the back-flushing guide (21) are connected to each other, rotatably disposed inside the filter housing (1, 3), and movable to execute adjustment movements between the filtration operation and the back-flushing by means of a rotary drive (5).
 4. The filtering apparatus according to claim 1, characterized in that a piston accumulator (13) is provided as a hydraulic accumulator that is rotatable around the cylinder axis together with the back-flushing guide (21), which is disposed on the one cylinder end (11).
 5. The filtering apparatus according to claim 1, characterized in that the filtering elements (9) can each be accommodated in an own element chamber (7) thereof, and which are disposed inside the filter housing (1) along a circular line forming a concentric circumference around the cylinder axis.
 6. The filtering apparatus according to claim 1, characterized in that the element chambers (7) include a first chamber hook-up (63), which is connected to the clean side (59) of the filtering element (9), and a second chamber hook-up (53), which is connected to the untreated side (55), and in that both of these hook-ups are open toward a main chamber of the filter housing (1) and into which the rotatable back-flushing guide (21) extends as a switching organ, the adjustment movements of which control the inflow and outflow of fluid to and from the first (63) and second chamber hook-ups (53) for the back-flushing operation.
 7. The filtering apparatus according to claim 1, characterized in that the back-flushing guide (21) includes, at an axial spacing from the piston accumulator (13) and from the opposite end thereto, an annular body (33) forming a radial projection with a circumferential radial seal (39), which, together with the wall (41) of the main chamber, divides said chamber into a filtrate part (35) with the filter outlet (43) and a non-filtrate part (37) with the filter inlet (45).
 8. The filtering apparatus according to claim 1, characterized in that the openings of the first and the second chamber hookups (63 and/or 53) are disposed on a wall (41) of the filtrate part (35) and/or non-filtrate part (37) of the main chamber forming a cylinder surface, and in that, with the change to back-flushing, the hook-up ends (73, 77) that project from the cylinder axis, respectively, from the inflow line (71) and outflow line (75), formed on the back-flushing guide, become congruent with the chamber hook-ups (63, 53), wherein the inflow line (71) constitutes the connection of the first fluid chamber (67) of the piston accumulator (13) to the first chamber hook-up (63) and the outflow line (75) the connection of the second chamber hookup (53) to a back-flushing outlet (27) of the main chamber.
 9. The filtering apparatus according to claim 1, characterized in that the back-flushing outlet (27) can be blocked and released by a valve apparatus (31).
 10. The filtering apparatus according to claim 1, characterized in that the valve control includes a valve that is actuated by a pressure means, preferably in form of a 5/2-way valve (93), which controls the connection to the fluid chamber (79) of the hydraulic accumulator (13), which can be pressurized with a pressure medium, and the pressure source.
 11. The filtering apparatus according to claim 1, characterized in that a further valve, preferably in form of a 3/2-way valve (95), by which the fluid chamber (79) of the hydraulic accumulator (13) can be connected to the pressure source, allows for an optional reduction of the media pressure inside the hydraulic accumulator (13).
 12. The filtering apparatus according to claim 1, characterized in that the fluid chamber (67) of the hydraulic accumulator (13) that accommodates the volume of the cleaned fluid can be filled via a flow-control means (69), which is disposed between the filtrate part (35) of the main chamber and the inflow line (71) of the back-flushing guide (21). 